Method of making concrete conduits



March 6, 1934. H. E. LlNnAs METHOD OF MAKING-CONCRETE CONDUITS Filed Apr A TTORNE Y March 6, 1934. H. E. LINDAs I METHOD 0F MAKING CONCRETE CONDUITS 2 Sheets-Shea `Filed April 4, 1932 A TTORNE Y Patented Mar. 6, 1.934 l 1,949,650 METHOD F MAKING CONCRETE CONDUI'I-IS Henry E. Lindas, Wichita, Kans. Application April 4, 1932, Serial No'. 603,138

3 Claims.

The present invention relates to a conduit core, and method for casting concrete conduit.

Various types of iniiatable cores have been devisedvfor the casting of concrete conduit and one of the principal diiculties in using a core of this type lies in the fact that the core has a tendency to adhere to the molded conduit when completed, and thus 'renders difiicult and sometimes impossible the withdrawal of the core.v

An object of the present invention is to make an improved and simplified core for the casting of. a conduit.

Another object is to improve 'the method of casting cementitious conduit. y In. order to attain these objects; there is provided, in accordance with one feature of the invention, an inflatable core constructed of rubber impregnated fabric or cords with the threads ofthe fabric or the cords normally disposed at an '9,0 angle of less than forty-five degrees tofa. longitudinal plane bisecting the core.

This and other features of the invention, will' be more fully brought out in the following deription' and the accompanying drawing, where- I Figure l is a view in-side elevation of an-end portion of a conduit core embodying the present invention, parts being broken away to show the structure of the device. s

Figure 2 is a sectional view on the line 2--2 of Figure 1.

Figure 3 is a 4sectional View of a split retain ing collar.

Figure 4 is a view in side elevation' ofthe collar a5 shown in Figure 3.

Figure is a diametric view of a section of the gk 'fabric used in constructing the expansible core Lwith the threads of the fabric in normal position. Figure 6 is a view,vsimi1ar to Figure 5, with the threads in the positionthey occupy after expansion ofthe core. y

Figure 7 is a sectional view through a quadruple trench showing therein successive stages in the formation of a conduit in accordance with the present invention.

Figure8 is a view in side elevation of a def ated core member, the central portion thereof being broken away, the dotted lines indicating the diametric expansion anchl longitudinal contraction which takes place upon inflation ofthe core. Figure 9 is a view inside elevation of an expanded core in position in a conduit,.the conduit being shown sectionally, the center portion being broken away.

Figm-e 10 is a sectional View of a condit showing an expansion joint in section thereon, portions of lthe expansion joint being broken away; and

Figure 11 is a view in'perspeotive of an end compression and retaining member. g l V Referring to the drawing in detail, a core mem- 00 ber A is constructed of superposed layers 1 and 2 of fabric or cord material having thethreads or cords thereof vdisposed at an4 angle of approximately thirtydeg'rees, with a plane bisecting thelongitudinal axis of the core. Figure 5 shows the 65 cords or threads in their normal position, and l Figure 6 shows them in the position they occupy when the core is inflated. Thesecords or threads are impregnated with and imbedded in rubber 3 i unvulcanized rubber 6 is then placed over the 50 outer face of the head 5 and the open end of the core A is drawn closely around the threaded stem member 4' by means of a split collar 7 which is drawn into close retaining position with the open end of the core, as by means gf screws 8 and 9 to B5 rmly grip theend `of the core to compress it tightly against the threaded exterior of the tubularmember 4. A mass of unvulcanized rubber 10 is then packed around the core between the inner face of the collar 7, and the end of the core. A second mass l1, of unvulcanized rubber, is then placed on the outer face of the collar 7, the word i outer being used to refer to the direction toward the open end of-the core, and the word inner Ato the direction toward the Abody of the core. `A skirt' member 12 having a tapered inner surface adapted tov coincide with the tapered outer surface of the collar 7, is provided witha central opening 13, of a size to have y a free slidable ilt over the threaded stem portion 4. A nut 14 is then threadedly mounted on the stem 4 and isdrawn down to force the skirt member 12 inwardly to exert a cam-like compressing action on the collar 7. f

When thus' provided with'threaded end mem- 105 bers, successive lengths of core may be connected together by mea'siof ordinary pipe unions 15.'

It is imperative, of course, that the cementitious material, such as concrete, of'which a conduit is formed around thev present type of core, be not quired points, and sleeves 16 arev also over each vof the connections 15 between core sec-y allowed to surround the end portion of the cores and the unions connecting successive lengths of conduit. In order to prevent these connections from becoming imbedded in the cementitious conduit material, sleeves 16 which may be of metal tubing, having an internal diameter equal to that of the core when expanded, are slipped over each of the connections of successive lengths of core when completed. These joint enclosure members are of a length to overlap the core on each side of the connection, as indicated at 17, so that the expanded core iills and seals these tubular connections against the entrance of conduit material therein. It is necessary and desirable to provide for exlpansion in the conduit andthis may be accomplished by means of ordinary steam-line expansion joints B, such as shown in Figure 10. These expansion joints may be inserted at distances determined by the engineer in charge of installation and will depend, of course, on the nature of the soil in which the conduit is buried and 'the probable temperature differences which will be encountered. The well knownvtype of joint illustratedcom'prises a sleeve 18, which is slidably mounted in a casing 19 inwhich a packing ring, not shown, is held in close contact with the sleeve 18 by means of a collarl 20, held in position by means of bolts 21 and nuts 22.

The expansion joint used should be for the same pipe size as the diameter of the core when inflated, and, if desired, short lengths of pipe 23 and 24 may be threadedly inserted, one in each end of the expansion joint, to more rmly bind the expansion joint to Athe sections of concrete conduit which it connects. These expansion joints may be slipped on over the core while the core` is deflated and positioned at desirable intervals. When the core is iniiated, it will fill, and thereby seal, the ends of the joints or the pipes 23 and 24 against the admission of the cementitious conduit material.

Operation In forming a conduit in accordance with the present invention, a trench 25 (see Figure 7)v is dug and is lined with side boards 26 and 27.. 'Ihe core A is then laid alongside the trench and expansion joints B are slipped onto the core at remountd tions.' The core vis then lpumped full of iiuid, which may be either water or air, to the required pressure to expand the core to the dotted line position shown in Figure 8. Conduit'material 28, which may be concrete, is then poured into the trench 25 and the core A is partially embedded in the concrete while soft, as indicated in the secf ond trench from the left in Figure 1. The core is thereafter covered with a layer of concrete 29 and corner forming beads 30 and 31 are pressed into the sides of the concrete to round out the upper side thereof. The concrete is permitted to harden, whereupon the fluid filling the core A is pumped out. This permits the core to contract to its original diameter and to elongate, as shown in solid lines in Figure 8. This contraction and elongation, due to the inherent elasticity of the titious material.

asphalt or tar, as indicated in Figure 10, while the sleeves 16 and 17, illustrated in Figure 9, are covered with concrete and remain imbedded therein after withdrawal of the core.

The core is simple and relatively inexpensive to manufacture, has a uniform rate of expansion up to a point where the cords or threads of which it is fabricated reach an angle of approximately fifty-two degrees to a plane passing through the longtiudinal axis of the core, and thereafter, resists further expansion. The lateral contraction of the core, upon deflation, combined with the elongation thereof, frees the core from the con-.- duit walls and permits its easy withdrawal, thereby overcoming what has heretofore been one of the principal diiculties attendant upon the use of inflatable cores in the making of concrete conduit.

I claim:

1. The method of making concrete conduit,

which comprises molding plastic cementitious material around a tubular conduit core having the wallsthereof of rubber with reinforcing fabric/ mentitious material after said cementitius material has hardened.

2. The method of building a concrete conduit comprising inserting an elongated uid tight elastic core having restricted ends into oppositely disposed ends of thin stiff tubes and locating the same so that only the opposed ends of the tubes and ends of the core overlap, encasing both said tubes and inated core in wet concrete, drying the concrete and deati'ng and removing the core*- through one of said tubes.

3. The method of making concrete condut, which comprises covering a tubular core niember, materially expansible diametrically and contractible longitudinally on expansion, lwith wet cementitious material while said tube is in an inated conduition. allowing said material to harden around the core while the core is expanded, then deating the core causing the core to contract diametrically and expand longitudinally suflcient to separate the core from the interior of the hardened cementitious material and afterwards withdrawing said core from, said hardened cemen- HENRY E. L INDAs. 

